The present invention relates to a control device for an engine, particularly to a control device which controls an engine based on an operating state of a vehicle.
Conventionally, devices for controlling, when a behavior of a vehicle becomes unstable due to slippage etc., the behavior of the vehicle toward a safe direction (e.g., sideslip preventing device) are known. Specifically, engine output control devices are known, which include a Dynamic Stability Control (DSC) and a Power-train Control Module (PCM). The DSC outputs a torque limit value to reduce an output of an engine so as to suppress slippage of wheels, and to limit the output of the engine so as to suppress torque steering according to a steering angle detected by a steering angle sensor. The PCM performs an output control of the engine based on the torque limit value outputted by the DSC. For example, JP2007-113408A discloses such a device.
On the other hand, as opposed to such a control for improving safety under a traveling state where the vehicle behavior becomes unstable, vehicle operation control devices are known, which control a load on front wheels (drive wheels) by adjusting a deceleration when the vehicle corners, so that a series of operations performed by a driver (braking, turning of steering, accelerating, and turning back the steering, etc.) in a normal traveling state of the vehicle becomes natural and stable. For example, JP2011-088576A discloses such a device.
Further, vehicle behavior control devices are known, which reduce a drive force of a vehicle according to a yaw rate related amount (e.g., yaw acceleration) corresponding to a steering operation by a driver, so as to promptly produce a deceleration in the vehicle when the driver starts the steering operation, and promptly apply a sufficient load on front wheels (drive wheels). For example, JP2014-166014A discloses such a device. According to such a vehicle behavior control device, by applying the load on the front wheels when the steering operation is started, a friction force between the front wheels and a road surface increases and a cornering force of the front wheels increases, and therefore, turning performance of the vehicle in a start of entering a curve improves and responsiveness to a turning operation of the steering improves. Thus, a vehicle behavior intended by the driver is achieved.
When mounting the vehicle behavior control device of JP2014-166014A on the vehicle, it may be considered to apply the DSC of JP2007-113408A. Specifically, the DSC may be applied to limit the output of the engine according to the steering angle detected by the steering angle sensor so as to suppress the slip and torque steering, and reduce a drive force of the vehicle according to a yaw rate related amount calculated based on the steering angle. Thus, a deceleration is produced in the vehicle when a driver starts a steering operation, and a load is applied on front wheels.
Meanwhile, with the vehicle behavior control device described in JP2014-166014A, to accurately realize the vehicle behavior intended by the driver, the drive force of the vehicle needs to be reduced promptly in response to the steering operation. However, in the case of reducing the drive force of the vehicle by the DSC according to the steering operation as described above, the DSC first calculates a required deceleration and a required drive force reduction amount corresponding to the steering angle detected by the steering angle sensor, and outputs the calculated deceleration and the calculated drive force reduction amount to the PCM. Then the PCM needs to cause the engine to output based on the received deceleration and drive force reduction amount. Thus, after the steering operation is detected by the steering angle sensor, the steering sensor and the DSC, and further the DSC and the PCM need time to communicate with each other before the PCM performs the output control of the engine. Therefore, sufficient responsiveness to the steering operation cannot be secured. As a result, the vehicle behavior intended by the driver cannot accurately be achieved.